Tetrafluoroethylene copolymers



enema Apr. 26, 1949 TETRAFLUOROETHYLENE COPOLYMERS William E. Hanford,Easton, Pa., and John R. Roland, Jr., Wilmington, Del., assignors to E.I. du Pont de Nemours & Company, Wilmington, Del., a corporation ofDelaware No Drawing. Application August 28, 1945, Serial No. 613,212

' 12 Claims. (01. 260-86) This invention relates to polymeric materialsand more particularly to polymers obtained from tetrafluoroethylenewThis application is a continuation in part of our application Serial No.463,410 filed October 26, 1942 now abandoned.

The polymerization of tetrailuoroethylene has been described previously.The polymerization of this compound has been eflected, for example, byallowing tetrafluoroethylene to stand at room temperature or above atsuperatmospheric pressure in the presence of certain polymerizationcatalysts. The polymerized product heretofore obtained is a hard, tough,infusible solid which is insoluble in and unattached by inorganic acids,alkalies, and organic solvents. While this combination of properties isvery desirable for a great many applications, these very properties makethe polymer unavailable for other uses.

This invention has as an object new and useful compositions of matter. Afurther object is valuable high molecular weight polymers comprisingtetraiiuoroethylene', A still further object resides in a process forobtaining these polymers in high yields. Other objects will appearhereinaiter.

The above objects are accomplished by the process more particularlydescribed below which comprises polymerizing in the presence of oxygenor a peroxy compound as a catalyst a mix-- ture of tetrailuoroethyleneand another polymerizable organic compound having at least one eth-Ylenic double bond. We have discovered that valuable macromolecularcopolymers can be thus obtained which, because of their differentphysical properties, are adapted to a number of uses to which thepolymerized tetrafluoroethylene itself is unsuited.

The operating conditions described herein, e. g., pressure, employed forthe preparation of a given copolymer, will, in general, depend on thephysical properties of the comonomer being used. That is, to obtainpolymers of suitable molecular weight for some purposes, it is necessaryto maintain an appreciable concentration of the polymerizable monomersin the polymerization phase. Thus, in the case of normally liquidcomonomers, such as vinyl carboxylates, e. g., vinyl acetate, and estersof alpha-beta-unsaturated monocarboxylic acids, e. g., methylmethacrylate, adequate monomer concentrations are achieved at relativelylow tetrafluoroethylene pressures, hence the polymerization can becarried out satisfactorily under pressures ranging up from 3 to 1000atmospheres or more. While the process of this invention is gels totough, high-softening thermoplastics.

operable at pressures as low as 3 atmospheres, with normally gaseouscomonomers, such as olefinic hydrocarbons, e, g., ethylene andisobutylene, and halogenated ethylenes, e. g., vinyl fluoride, vinylchloride, chlorotrifluoroethylene etc., higher pressures, for example,at least 20 atmospheres are desirable to achieve such monomerconcentrations as will lead to high molecular weight polymers.

Operable reaction temperatures range from as low as 10 C. in someinstances to as high as 300 C. in other instances, but, as in the caseof pressure, the particular temperature selected within this range willdepend on the nature of the comonomer with which the tetrafluoroethyleneis copolymerized. For the preparation of copolymers oftetrafluoroethylene with normally liquid unsaturated hydrocarbons, e.g., styrene and butadiene, the polymerization reaction is generallycarried out at lower temperatures, e. g., 10-80 C. and at pressures ofat least 10 atmospheres.

The properties of the tetrafluoroethylene copolymers of this inventionvary considerably with the comonomer employed, ranging from viscous Ingeneral, they differ from the homopolymers of each comonomer inexhibiting abnormally high tensile strengths, and in the case of solublepolymers, abnormally high viscosity in solution. The polymers alsopossess excellent chemical and thermal stability, good electricalproperties and low to negligible flammability.

Those copolymers containing from 5% to about 95% of tetrafiuoroethylene,based on the combined weight of the tetrafluoroethylene and otherethylenically unsaturated compound or compounds previously mentioned,are the most valuable since in this range is obtained the maximumdifierentiation in properties from those of the unmodified homopolymers.

In the case of the copolymers of tetrafluoroethylene with ethyleneparticularly valuable co-, polymers are obtained by using the ethylenein' containing from to 40% of tetrafluoroethylene by weight diiier fromthe ethylene homopolymer in possessing higher softening points,decreased solubility, increased solution and melt viscosity, and inbeing more inert to chemical reagents. In addition, they appear to beremarkably strong compared with the ethylene homopolymer.

Tetrafluoroethylene isobutylene copolymers containing from 55% to 80%tetrafluoroethyleneby weight are stiff, tough, transparent totranslucent, nonresilient but flexible thermoplastic resins, which havesoftening points ranging from 100-200 C. and tensile strengths rangingfrom 3500-6000 lbs./sq. in., again remarkably higher than those ofeither parent homopolymer. In contrast to the ethylene interpolymersthese copolymers exhibit considerable plastic flow at temperatures wellbelow their true softening points. These copolymers can be dissolved inhot solvents above about 120 C. Copolymers of tetrafiuoroethylene withisobutyiene containing less than about 55% tetrafluoroethylene havelower softening points, and, in general range from transparthan bymaterial difierences in results as the pres.- sure rises indefinitelybeyond the minimum value required to yield the desired results. Thepresence of water leads to a smoother process and aids in controllingthe reaction which otherwise may take place too violently. The reactioncan be run in a closed system if desired, but it is advantageous toinject, either batchwise or continuously, a mixture oftetrafluoroethylene and the unsaturated compound in the desiredproportions as the reaction progresses. Since tetrafiuoroethylene is agas, the course of the reaction may be followed by the dro in pressurein the reaction container, and cessation of reaction is indicated bycessation of the pressure drop. Depending on the polymerizingcharacteristics of the particular unsaturated compound which ent viscousgels to low melting (below 100 C.)

thermoplastic resins.

Copolymers 'of tetrafluoroethylene with certai completely halogenatedolefins, e. g., chlorotrifluoroethylene, resemblepolytetrafluoroethylene in being inert to chemical reagents, but possessthe remarkable advantage over polytetrafluoroethylene of beingextrudable and generally more workable in the molten state. Thus, thesecopolymers represent a class of materials having the general propertiesof polytetrafluoroethylene, but applicable in certain uses to-whichpolytetrafluoroethylene cannot be applied because of the difliculty ofworking it in the molten state.

Copolymers of tetrafluoroethylene with halohydroethylenes, e. g., vinylfluoride, vinyl chloride, 1,1-difluoroethylene, etc., are in generalsoluble, high softening tough thermoplastics. While their softeningtemperatures and thermal stabilities are generally intermediate betweenthose of polytetrafluoroethylene and of the homopolymer of thecomonomer, they possess surprisingly high dielectric constants which, incombination with moderately good power factors, make them a unique classof materials for high temperature chemically resistant dielectriinsulators.

is polymerized with the tetrafluoroethylene the operable temperaturesand pressures will vary somewhat widely as has been pointed outpreviously. The polymerizable compositions used in obtaining the presentcopolymers preferably consist wholly or in major amount of the mixtureof tetrafluoroethylene and'the other comonomers described above.

The invention is further illustrated by the following. examples in whichthe parts are by weight unless otherwise indicated;

Example I A stainless steel high pressure reactor having a capacity ofabout 400 parts by volume is flushed with oxygen-free nitrogen'andcharged with 25 parts of deoxygenated water, 1'75parts of tertiary butylalcohol, and 0.15 part of ammonium persulfate. The reactor is closed,evacuated, and then further charged with a mixture oftetrafiuoroethylene and ethylene having a mole ratio oftetrafiuoroethylene to ethylene of 1:0.79. The reactor is agitated andheated at C. while maintaining an internal pressure within the range of300-350 lbs./sq. in. by the periodic injection of the above indicatedmonomer mixture. After heating for 1.5 hours, the reactor is cooled, thepressure is released and the product is discharged. There is thusobtaineda tetrafluoroethylene/eth- I ylene copolymer in the form of athick slurry The copolymers of tetrafluoroethylene with vinylcarboxylates, e. g., vinyl acetate, are stiff thermoplastic resinshaving softening points which are higher than those of the correspondingpolyvinyl carboxylate. In general, the copoly-.

- mers are transparent and have good tensile which is coagulated bysteam distillation, The copolymer, when washed and dried, amounts to 52parts. The copolymer contains 61.9% fluorine which corresponds to a moleratio of tetrafluoroethylene to ethylene of 1:0.815..' A film of thecopolymer softens at 285 (2.: it has a tensile strength of 8000 lbs./sq.in. at 400% elongation, a power factor (1 kc.) of 0.1% and a dielectricconstant (1 kc.) of 2.7. Solutions of this copolymer can be obtained byheating the polymer in dimethyl glutarate, dimethyl adipate, diethyladipate, diisobutyl adipate, dimethyl azelate, dibutyl sebacate,dimethyl methadipate, dimethyl hexahydrophthalate, isophorone,benzophenone, or a. mixture of unsaturated cyclic ketones boiling withinthe range of 250-325 C. and containing 12 to 18 carbon atoms.Dispersions can be prepared by cooling solutions of th polymer untilgellation occurs and then vigorously stirring the gelled solution. I

Porous articles can readily be prepared by dissolving the polymer in asolvent,- such as camphor or a camphor-isofenchone mixture at elevatedtemperature, cooling the solution to solidify the mixture and finallyremoving by any convenient method, such as extraction or sublimation,the solidified material which functioned as the solvent at elevatedtemperature.

Polymers or lower molecular weight and lower melt viscosity canbeobtained by replacing a portion of the tertiary butyl alcohol withacetone,

methyl alcohol, ethyl alcohol or isopropyl alcohol.

These polymers are soluble in nitrobenzene, acetophenone and chlorinatedethyl benzene.

Example II A stainless steel-lined pressure reactor is charged with 100parts of oxygen-free water and 0.1 part of benzoyl peroxide; the pH isadjusted to 3.4 by the addition of aqueous formic acid. The loading ofthe reactor is conducted under an atmosphere of oxygen-free nitrogen.The reactor is closed and charged with a mixture of tetrafluoroethyleneand ethylene containing of the former by weight. The reactor is agitatedand heated to 75 C., and the pressure is maintained in the range 700-900atmospheres by the injection of a liquid mixture of tetrafluoroethyleneand ethylene containing 10% of the former by weight. When the pressuredrop ceases, the tube is cooled and discharged. There is obtained 30parts of a white polymer which contains 22.34% fluorine, or an averageratio of one C2F4 unit to 8.6 C2H4 units. This copolymer is completelysoluble in such solvents as hot xylene and hot tetrachloroethy-lene,thus being distinguished from pure polytetrafluoroethylene, which isabsolutely insoluble in such solvents. The polymer has an intrinsicviscosity (as defined in U. S. Patent 2,130,948) of 2.16 (0.125%solution in xyleneat 85 C.). The polymer can be pressed to a tough,clear, pliable film at 150 C., and 400 lbs/sq. in. The film has atensile strength, based on the original dimensions, of 2355 lbs/sq. in.and an elongation of 464%. Tough, transparent foils can be cast from a10% solution of the polymer in hot xylene; these foils exhibitremarkable clarity and resistance to tear.

Example I I I A silver-lined pressure reactor is charged with 100 partsof water, 30 parts of freshly distilled vinyl acetate, 2 parts ofdisodium phosphate dodecahydrate and 0.2 part lauroyl peroxide. Thereactor is then closed and there is added 20 parts of gaseoustetrafluoroethylene and then suflicient ethylene to raise the gaspressure within the reactor to 600 atmospheres. The reactor is agitatedand heated at 60 C. and the pressure is maintained in the range of840-980 atmospheres by the injection of additional ethylene. After eighthours the reactor is cooled and discharged to yield 42 parts of whitetough, rubbery polymer. The polymer contains 23.87% fluorine and 53.85%carbon corresponding to a molar ratio of vinyl acetatetetrafluoroethylene ethylene of 1 0.65 2. The polymer softens at 150-180C. and is soluble in hot xylene. The vinylacetate/tetrafluoroethylene/ethylene copolymers can be hydrolyzed toobtain modified polyvinyl alcohols.

Example IV A stainless steel high pressure reactor having a capacity ofabout 400 parts by volume is flushed with oxygen-free nitrogen andcharged with 200 parts of deoxygenated water and 0.2 part of benzoylperoxide. The reactor is closed and is further charged with 150 parts ofa mixture of tetrafluoroethylene and isobutylene having a mole ratio oftetrafluoroethylene to isobutylene of 2:1. The reactor is agitated andheated at 80 C. while maintaining an internal pressure within the rangeof 2700-2900 lbs/sq. in. by the periodic injection 01' additionalquantities of the terafiuoroethyleneisobutylene mixture indicated above.After a rereaction period of 15.5 hours the reactor is cooled, thepressure released and the product is discharged. The copolymer, whenwashed and dried, amounts to 130 parts and contains 51.6% fluorine whichcorresponds to a mole ratio of tetrafluoroethylene to isobutylene of1.2:1. Films are prepared by hot pressing the copolymer at 220 C.

Example V A stainless steel-lined pressure reaction vessel is chargedwith an aqueous emulsion consisting of 58 parts of copper-free distilledwater, 0.53 part of sodium hydroxide, 2 parts of oleic acid, 0.5 part ofa sodium salt of a sulfonated naphthaleneformaldehyde condensationproduct, 0.3 part of octyl mercaptan, and 0.5 part of ammoniumpersulfate. The reaction vessel is closed and parts oftetrafluoroethylene and 35 parts of 1,3-butadiene are added. The valveon the pressure reaction vessel is closed and the reaction mixture isheated for hours at 50 C. while rotating the reaction vessel end overend. The white latexlike emulsion is stabilized by the addition of 2parts of a 50% dispersion of a 55:45 eutectic mixture ofphenyl-alpha-naphthyl amine and diphenyl amine. The aqueous emulsion iscoagulated by the addition of dilute acetic acid and brine. Theresulting rubbery copolymer is washed with water on a corrugated rubbermill and finally dried on a heated smooth rubber mill. There is obtainedtwenty-nine parts of a rubber-like copolymer containing 17.5% fluorineby analysis, which corresponds to an average ratio of one C2F4 unit to6.2 C4Hc units.

The copolymer is compounded according to the following formula and curedfor thirty minutes at 145 C.

Parts Copolymer 10.0 Phenyl-alpha-naphthylamine 0.2 Carbon black 5.0Stearic acid- 0.2

Sulfur 0.2 Mercaptobenzothiazole 0.1 Zinc oxide 0.5

A snappy, resilient, rubber-like vulcanizate is obtained.

' Example VI A stainless steel-lined pressure reactor is charged with100 parts of water, 40 parts of freshly steam distilled styrene, and 0.4part of henzoyl peroxide. After closing the reactor, there is added 35parts of gaseous tetrafluoroethylene. The reactor is agitated and heatedat C. for five hours. The copolymer obtained after steam distillationand subsequent drying on a hot rubber mill is a brittle solid containing5.82% fluorine, or an average ratio of one C2F4 unit to 11.6 CaHa units.

Example VI] part of ammonium ,and 102 parts 01' vinyl fluoride.

actor is then cooled, the product is discharged. The copolymer, whenwashed and dried, amounts to 57 parts and is found to contain 60.6%fluorine which corresponds to a tetrafluoroethylene/vinyl chloridecopolymer having a mole ratio of tetrafluoroethylene to vinyl chloride01' 2.44:1.

Example VIII A stainless steel high pressure reactor having a capacityequivalent to about 400 parts of water is swept with nitrogen andcharged with 100 parts of deoxygenated Water and 0.2 part of benzoylperoxide. It is then closed, evacuated, and iurther charged with 52parts of tetrafluoroethylene The reactor is agitated and heated at 80 C.while maintaining an internal pressure within the range of 200-310 atms.by the periodic injection of deoxygenated water. The sum or the pressuredrops during nine hours is 450 atms. cooled, the pressure released, andthe product is discharged. The copolymer, when washed and dried, amountsto 83 parts and is found to contain by analysis 45.2%. oftetrafluoroethylene which corresponds to a tetrafluoroethylenezvinyl Astainless steel-lined pressure reactor is charged with 100 parts ofwater, 0.2 part of ammonium persulfate, 4 parts of borax, 30 parts of1,1-dichloroethyiene, and 100 parts of tetrafluoroethylene. The reactoris agitated and heated at 75 C. for six hours. The resulting product isa hard resin containing 2.18% fluorine, or 2.9% tetrafluoroethylene byweight.

Example X A silver-lined high pressure reactor is swept with oxygen-freenitrogen and then charged with 0.4 part of benzoyl peroxide and 200parts of deoxygenated water. The reactor is then closed,

evacuated and then further charged with 60 parts of tetrafluoroethyleneand 15 parts of 1,1- difluoroethylene through a valve. The reactor isagitated and heated to 80 C. The pressure within the reactor is thenraised to 3200 lbs./sq. in. i

by the injection of additional deoxygenated water. The temperature ismaintained at 80 C. and additional deoxygenated water is periodicallyinjected to maintain the pressure within the range of 3000-3200 lbs./sq.in. The sum of the individual'pressure drops during 9 hours reactiontime is 1600 lbs./sq, in. The reaction vessel is cooled to roomtemperature, the unreacted portionof the gaseous monomers is bled oil,and the contents of the tube are discharged. There is obtained 24 partsof a copolymer which contains 69.3% fluorine which corresponds to a.mole ratio of tetrafluoroethylene: 1,1-difluoroethylene of 1:1. A filmobtained by hot pressing the copolymer has a tensile strength of 3900lbs/sq. in. at 548% elongation, a temperature of zero tenacity of 231C., a dielectric constant (1 kc.) of 8.59 and a power factor (1 kc.) of0.0171. The copolymer is insoluble in hot nitrobenzene and in pressurereleased and the i The reactor is then 8 'hot iso'phorone but can beextruded into filaments when heated at 2910 C. under pressure. Example'XI 7 A stainless steel high pressure reactor is flushed withoxygen-tree nitrogen and charged with 200 cooled, the pressure isreleased and the product is discharged. The copolymer, when washed anddried amounts to 35 parts. The copolymer contains 7.07% chlorine whichcorresponds to a chlorotrifluoroethylene content 0! 56% or a mole ratioof tetrafluoroethylene to chlorotrifluoroethylene of 1:1. A colorlesstransparent fllm, obtained by ressing the copolymer at 240C. under apressure of 10,000 lbs., has a tensile strength of 3870 lbs./sq. in.,can be elongated 380% and has a modulus of elasticity of 0.0675x 10lbs/sq. in. The films are nonflammable and, 2

when heated under a tension of 20 lbs./sq. in., pull apart at atemperature of 217C, The polymer is insoluble in all organic solvents;it is much more workable than polytetrafluoroethylene.

' Example x11 A stainless steel lined high pressure reactor is chargedwith parts of water, 2 parts of disodium phosphate and 50 parts of vinylacetate. The air in the free space of the vessel corresponds to 0.075part of oxygen. The reaction vessel is closed and is further chargedthrough a valve with 25 parts of tetrafluoroethylene. The reactor isagitated and heated at C. for flve hours. It is then cooled, opened andthe contents removed. The unpolymerized vinyl acetate is removed. bysteam distillation and the copolymer is obtained as a light yellow solidcontaining 16.25% fluorine which corresponds to a ratio oftetrafluoroethylene to vinyl acetate of 1:427.

.The copolymer melts at C. and is soluble in hot dioxane, xylene,benzene, pyridine, and

chloroform and can be hydrolyzed to a modified polyvinyl alcohol.

Example XIII A stainless steel-lined pressure reactor is charged with100 parts of water,50 parts oi freshly distilled vinyl propionate, and0.4 part of benzoyl peroxide. The pH is adjusted to 3.5 by the additionof aqueous formic acid. The reactor is .then closed and there is added37 parts The reactor is agitated and heated at 80 C, for five hours. TheI of gaseous tetrafluoroethylene.

Example xiv A stainless steel-lined pressure reactor is charge with 100parts of water, 0.2 part of ammonium persulfate, 2 parts of borax, and30 parts 01' freshly distilled methyl methacrylate. The reactor is thenclosed and there is then added 100 parts of tetrafluoroethylene. Thereactor is agitated vigorously and heated at 80 C. for six hours. Oncooling and opening the tube there is obtained 22 parts of whitegranular polymer containing 4.61% fluorine.

Example XV A silver-lined pressure reactor is charged with 100 parts ofwater, 34 parts of dimethyl-(vinylethynyl) -carbinol, and 0.2 part ofbenzoyl peroxide. The pH of the reaction mixture is adjusted to 3.4 bythe addition of aqueous formic acid. The reactor is then closed andthere is added 30 parts of tetrafluoroethylene. The reactor is thenheated to 80 C. and agitated for six hours. The product is washed bysteam distillation and is then completely dissolved in hot acetone, thusindicating that it contains no polytetrafluoroethylene, which isinsoluble in acetone. Evaporation of the acetone under .iminishedpressure leaves a hard yellow resin which contains 3.36% fluorine.

The polymerizable unsaturated organic compounds useful in forming thepresent copolymers with tetrafluoroethylene are characterized by theirability to undergo polymerization with tetrafluoroethylene to formmacromolecular polymers. Examples of such compounds are the monoethylenic hydrocarbons, such as ethylene, propylene, isobutylene, andstyrene; halogenated compounds such as 1, 1-difluoro-2-chloroethylene,trifiuoroethylene, chlorotrifluoroethylene, hexafluoropropene, andparticularly the vinyl halides such as vinyl fluoride, vinyl chloride,and vinyl bromide; vinyl carboxylates, such as vinyl formate, acetate,vinyl benzoate, and vinyl esters of higher aliphatic carboxylic acids;esters, nitriles, amides, anhydrides, and acid halides of alphamethylene monocarboxylic acids such as methyl rnethacrylate, methylacrylate, methylalpha-chloroacrylate, acrylonitrile, methacrylic amides,methacrylic acid anhydride, and methacrylic acid fluoride; vinyl etherssuch as vinyl ethyl ether and vinyl butyl ether; vinyl ketones, such asvinyl methyl ketone and vinyl phenyl ketone; N-vinyl compounds, such asN-vinyl succinimide, N-vinylphthalimide and N-vinyl carbazole; theesters of vinylene dicarboxylic acids, such as dimethyl fumarate anddiethyl fumarate; compounds having more than 1 ethylenic double bond,such as butadiene, isoprene, 2-fluoro-1,3-butadiene, 2-chloro-1,3-butadiene, 2-cyano-1,3-butadiene, and cyclopentadiene; andcompounds containing acetylenic unsaturation in addition to theethylenic double bond, for example, monovinylacetylene,divinylacetylene, and vinyl (ethinyl) -carbinols. Of the classes ofpolymerizable unsaturated compounds disclosed above, those which containa terminal ethylenic double bond, i. e., having group wherein a: and yare hydrogen or fluorine, are preferred because they copolymerize mostreadily with tetrafluoroethylene. 'I'etrafluoroethylene can beeffectively copolymerized with one or more of the above polymerizablecompounds to obtain 2-,3-, or multicomponent copolymers. Of the 3-component copolymers, the tetrafluoroethylene chlorotrifluorethylenevinyl fluoride and tetrafluoroethylene vinyl fluoride vinyl chloridecopolymers are particularly valuable because they are soluble insolvents such as acetone and clear films can be obtained from theirsolul0 tions. These clear fllms are suitable for use as photographicfllm bases.

It is possible to carry out the reaction in the presence of organicsolvents instead of or in additlon to water. Examples of solvents ofthis kind are hexane, octane, isooctane, cyclohexane, methylcyclohexanes, methyl cyclopentanes, benzene, toluene, xylenes, acetone,methanol, ethanol, isopropanol, tertiary butanol, dioxane, and tertiaryamyl alcohol.

Finely divided solids which serve as fillers can be included in thepolymerization mixture, and the polymerization can be carried out intheir presence. Examples of such fillers include pigments, such astitanium oxide and carbon black. metals, such as copper, aluminum andiron powder, and other finely divided materials such as mica. glass andasbestos. These and similar materials can also be added to the preformedpolymers.

The peroxy compounds used in the practice of this invention arecompounds containing the peroxy linkage -0-0-. Examples of thesecompounds are acyl peroxides, such as dibenzoyl peroxide, benzoyl acetylperoxide, dilauroyl peroxide, diacetyl peroxide, and dipropionylperoxide; dialkyl peroxides, such as diethyl peroxide, di-(tertiarybutyl) peroxide and dipropyl peroxide; hydrogen peroxide; inorganicperoxides in combination with an anhydride of an organic acid such asbarium peroxide with propionic anhydride, zinc peroxide, with butyricanhydride, and magnesium peroxide with acetic anhydride; and salts ofnon-metallic inorganic per-acids, such as ammonium persulfate, potassiumpersulfate and sodium persulfate. The catalyst should be used in anamount in excess of 0.001% based on the total weight of monomers andpreferably there is employed between 0.01% and 1% and not more thanabout 5% of the catalyst.

The tetrafluoroethylene employed in the practice of this inventionshould be reasonably pure and should be substantially free of acidicsubstances such as HCl and HF, and should be reasonably free of oxygen.Although oxygen is a catalyst in the small amounts indicated in thepreceding paragraph, larger proportions of oxygen have an adverse effectupon the reaction.

This polymerization reaction can be carried out in continuous fashion ifdesired. For example, a mixture of reactants can be passed continuouslythrough a zone which is maintained at reaction conditions, and which canbe provided with baflles, stirrers, or other means of agitation.'Alternatively, the catalyst can be injected into the system which ispassing through the reaction zone. 'In some cases, advantage may bederived by adding one or more of the polymerizing reactants to themixture in the reaction zone. Particularly valuand economy of operation,accurate control of the reaction and of the proportions of reactants,and flexibility of operation.

The equipment employed in carrying out this invention must be ofsuflicient strength to withstand the pressures and temperaturesemployed. That portion of the equipment which comes in actualcontactwith the polymerizing system must be fabricated of or lined witha material which ings.

will not rapidly catalyze the decomposition of the peroxy compound, orwhich will not be rapidly corroded or otherwise affected by any of thecomponents in the polymerizing system. Suitable anaterials includesilver, aluminum, tin, enamel, glass, stainless steel, monel metaLandnickel. as in the case of the polymerization of tetrafiuoroethylenealone using organic or inorganic peroxygen compounds as catalysts,reaction vessels constructed of mild steel can also be used for thecopolymerization of tetrafluoroethylene. It is preferable that thereacting system be equipped with some means of providing agitation.

The polymerized products of this invention are adapted to a wide varietyof uses. For example, they can be molded under elevated temperature andpressure into films, foils, tapes, and massive articles; Many of thelatter are exceptionally hard and tough, and can be employed asbearings, gears, bushings, pump pistons and in general for thoseapplications where hard high softening materials are desirable. They canbe Just ' said terminal ethylenic double bond is the sole fabricatedinto cellular or expanded forms which are particularly useful inapplications where spongy, resilient articles having communicating poresare desired. They are useful as adhesives, e. g., as a binder forparticles of carborundum or other abrasive materials in abrasivecompositions, for glass and silica in insulating forms and for iron orother magnetic materials in coil cores. These polymers can also befabricated into gaskets and container closures. They can be employed aselectrical insulators, such as spacer material for cable construction,as stopofl and mask materials combining insulating and corrosionresisting properties for use in plating baths, for wire coating bywrapping on the wire as a tape or yarn, or by coating the wire by meltextrusion or solution coating. Films of the polymers canbe employed asdielectrics for condenser construction, spacers for storage batteries,etc. Containers and metallic objects in general can be lined or coatedwith films of the polymers, either by solution coating or by pressingand baking a film on the object, to furnish moisture resistant,impervious, corrosion resistant coat- Flexible tubing can be fabricatedby melt or solution extrusion or by melt-sealing a tape into acylindrical form. The polymers can be spun into useful fibers by melt orsolution extrusion techniques, and these can be oriented by drawing, andcan be knitted or woven into a variety of fabrics. Large monoflls can beprepared, for example, by melt extrusion, and are useful as brushbristles. By solvent casting techniques, films valuable as wrappingfoils, etc. can be prepared. These polymers can also be used for coatingelectrical resistance wires.

As many apparently widelydifferent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that we do not limit ourselves to the specific embodimentsthereof except as defined in the appended claims.

We claim:

1. A composition of matter comprising the polymerization product of amixture of tetrafluoroethylene and another polymerizable unsaturatedorganic compound containing a terminal ethylenic double bond, saidmixture containing the tetrafiuoroethylene in an amount of from 5% to95% of the combined weight of the tetrafluoroethylene and said compoundcontain,- ing a terminal ethylenic double bond.

2. The composition set forth in claim 1 in which ethylenic double bondcontained in the organic compound.

3. The composition set forth in claim 1 in which said organic compoundis aliphatic and in which said terminal ethylenic double bond is thesole ethylenic double bond.

4. The copolymerset forth in claim 1 in which said polymerizable organiccompound is an unsaturated hydrocarbon containing a CH2=C group.

5. The copolymer set forth in claim 1 in which said polymerizableorganic compound is a halogenated ethylene.

6. The copolymer set forth in claim 1 in which said polymerizableorganic' compound is ethylene;

7. The copolymer comprising the polymerization product of a mixture of'tetrafiuoroethylene and ethylene which contains the tetrafiuoroethylenein an amount of from 15% to 00% of the combined weight of thetetrafluoroethylene and ethylene.

8. A process for obtaining copolymers which comprises, heating in thepresence of a catalyst to polymerizing temperature under a pressure ofat least 3 atmospheres a mixture of tetrafiuoroethylene and anotherpolymerizable, un-

saturated organic compound containing a terminal ethylenic doublebond,said mixture containing the tetrafluoroethylene in an amount offrom 5% to of the combined weight of the tetrafluoroethylene and saidcompound contain-, ing a terminal ethyienic double bond, said catalystbeing selected from the group consisting of peroxy compounds and oxygenand being present in said mixture in an amount of from 0.001%.

to 5% of the combined weight of the tetrafluoroethylene and saidcompound. I

9. The process set forth in claim 8 in which said polymerizable organiccompound is an unsaturated hydrocarbon containing a CH2=C group.

10. The process set forth inciaim 8 in which said polymerizable organiccompound is a halogenated ethylene.

11. The process set forth in claim 8 in which said polymerizable organiccompound is ethylene.

12. A process for obtaining a copolymer which comprises heating from 35C. to C. in the presence of a catalyst and under a pressure of at least20 atmospheres a mixture of'tetrafluoroethylene and ethylene whichcontains the tetrafluoroethylene in an amount of from 15% to 90% of thecombined weight of the tetrafluoroethylene and ethylene, said catalystbeing selected from the group consisting of peroxy compounds and oxygenand being present in said mixture in an amount of from 0.001% to 5% ofthe combined weight of the tetrafluoroethylene and ethylene.

wmusu E. HANFORD. JOHN R. ROLAND, .111.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

